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This case can been seen when creating the lease with the same objects passed. [ 605.515097] 2 locks held by testapp/3337: [ 605.519027] #0: (&dev->mode_config.idr_mutex){......}, at: [<ffff0000085f1664>] drm_mode_create_lease_ioctl+0x384/0x858 [ 605.530045] #1: (&dev->mode_config.idr_mutex){......}, at: [<ffff0000085f11bc>] drm_lease_destroy+0x2c/0x110 Which was causing the process to hang: [ 605.398827] [<ffff0000080856cc>] __switch_to+0x94/0xa8 [ 605.404030] [<ffff000008c05d00>] __schedule+0x1b0/0x698 [ 605.409322] [<ffff000008c06224>] schedule+0x3c/0xa8 [ 605.414260] [<ffff000008c06628>] schedule_preempt_disabled+0x20/0x38 [ 605.420677] [<ffff000008c07370>] mutex_lock_nested+0x158/0x340 [ 605.426572] [<ffff0000085f11bc>] drm_lease_destroy+0x2c/0x110 [ 605.432389] [<ffff0000085cecf0>] drm_master_put+0xc0/0xc8 [ 605.437845] [<ffff0000085f175c>] drm_mode_create_lease_ioctl+0x47c/0x858 [ 605.444612] [<ffff0000085d4460>] drm_ioctl+0x198/0x448 [ 605.449811] [<ffff000008201134>] do_vfs_ioctl+0xa4/0x748 [ 605.455192] [<ffff000008201864>] SyS_ioctl+0x8c/0xa0 [ 605.460216] [<ffff000008082f4c>] __sys_trace_return+0x0/0x4 drm_mode_create_lease_ioctl() calls drm_lease_create() which acquires a lock on dev->mode_config.idr_mutex. In case of failure, drm_lease_create() calls drm_master_put() which in turn tries to acquire the same lock when calling drm_lease_destroy(). v2: - Reverse the order at exit in case of fail, so that unlocking takes place before dropping the reference. - Include detail information about deadlock (Daniel Vetter) Signed-off-by: Marius Vlad <marius-cristian.vlad@nxp.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: https://patchwork.freedesktop.org/patch/msgid/20171213181048.32719-1-marius-cristian.vlad@nxp.com
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.